Mechanical face seals are used on various types of machines and equipment, such as pumps, compressors and gear boxes, which have rotating shafts and a sealing chamber adjacent the shaft wherein a fluid in the sealing chamber is prevented from leaking therefrom. Such mechanical seals include a pair of adjacent seal rings having opposing seal faces which define a sealing region therebetween. One of these seal rings typically is mounted on the shaft so as to rotate therewith while the other seal ring is non-rotatably mounted on a seal housing. The fluid being sealed is disposed on one edge of the sealing region, wherein the opposing seal faces at least reduce leakage of the sealed fluid across the sealing region.
Most liquid seals operate with the seal faces rotating in contact. However, due to asperities in the seal faces, some leakage may occur. In gas seals, the seal faces often are provided with grooves or recesses to generate hydrodynamic lifting forces. In this regard, the sealing faces typically separate a small distance wherein a thin film of fluid forms between the seal faces to lubricate the seal faces and reduce wear therebetween. Additionally, the grooves or recesses may pump the fluid film toward the fluid being sealed to reduce leakage of the sealed fluid.
With respect to the specific constructions of mechanical seals, one representative mechanical seal is disclosed in U.S. Pat. No. 6,446,976 (Key et al), the disclosure of which is incorporated herein in its entirety by reference. In this mechanical seal, one of the seal faces includes a plurality of concentric shallow annular grooves which preferably are disposed near the seal ring diameter that is farthest away from the fluid being sealed. In general, the basic construction of mechanical seals and the use of relatively rotatable seal rings are well known, and a detailed discussion of such mechanical seals is not required herein.
Also, a wide variety of seal face patterns are well known to the skilled artisan. For one such design, U.S. Pat. No. 5,834,094 (Etsion et al.) discloses the use of micropores in a seal face. U.S. Pat. Nos. 5,952,080, 6,002,100 and 6,046,430, also to Etsion, are all related to this patent, while U.S. Pat. No. 6,341,782 (Etsion) was subsequently directed to these micropore features. The disclosures of these references are incorporated herein in their entirety by reference. As to the specific micropores disclosed therein, such micropores are circular in plan view when viewing the seal face so as to either define concave or conical dimples or pockets. However, disadvantages have been associated with these micropores as discussed hereinafter.
In view of the foregoing, it is an object of the invention to overcome disadvantages associated with prior art mechanical seals such as the afore-mentioned micropores.
The invention relates to a tapered channel macro/micro feature for mechanical face seals, as well as a mechanical seal or seal ring incorporating such feature. The mechanical seal generally has a pair of coaxially aligned seal rings which are relatively rotatable during rotation of a rotating shaft. The seal rings have opposing seal faces that define a sealing region therebetween which prevents leakage of a fluid along the shaft.
At least one of the seal faces includes a plurality of a tapered channel macro/micro features which are distributed over the seal face, preferably in a plurality of circumferentially extending, annular rows. The rows of the tapered channels have concentrically increasing diameters. Preferably, the tapered channels of each row are radially staggered from one annular row to the next to provide a greater distribution of the tapered channels over the seal face.
The tapered channels serve as hydrodynamic lift features that generate a hydrodynamic lift which provides a stable separation of the seal faces that permits formation of a fluid film between the seal faces. Rather than the fluid film being generated solely by the static pressure of the fluid being sealed, the hydrodynamic lift features generate lift dynamically during shaft rotation to provide a lift load which is stable.
Testing of these unique macro/micro feature shows that it is possible to achieve a reduction in friction of 65%, significantly lower face temperature, exhibit debris resistance, show low to zero measureable leakage, and low to zero wear when compared to an untextured seal face. The term macro/micro feature is used to describe a feature that has a depth to size ratio, h/L (described hereinafter relative to FIG. 2), which is an order of magnitude smaller than current dimple configurations such as those disclosed in the Etsion patents referenced above, which is well below what may be considered useful from a performance standpoint based upon such prior art. This new macro/micro feature, preferably a tapered channel, demonstrates significant cavitation affects as well as hydrodynamic load support. These features are believed to be responsible for or contribute to this features' low leakage as well as its low friction/wear characteristics.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.